From b50c39ca4a87318f22999c9194b3fa63a371f111 Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Fri, 31 May 2019 20:11:26 +0200
Subject: [PATCH] Change size of preallocated buffer for pk_sign() calls

---
 library/x509write_crt.c | 12 +++++++++++-
 library/x509write_csr.c | 13 ++++++++++++-
 programs/pkey/pk_sign.c | 12 +++++++++++-
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 4cdb941a1..905de4cfa 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -49,6 +49,16 @@ static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }
 
+/*
+ * For the currently used signature algorithms the buffer to store any signature
+ * must be at least of size MAX(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)
+ */
+#if MBEDTLS_ECDSA_MAX_LEN > MBEDTLS_MPI_MAX_SIZE
+#define SIGNATURE_MAX_SIZE MBEDTLS_ECDSA_MAX_LEN
+#else
+#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
+#endif
+
 void mbedtls_x509write_crt_init( mbedtls_x509write_cert *ctx )
 {
     memset( ctx, 0, sizeof( mbedtls_x509write_cert ) );
@@ -338,7 +348,7 @@ int mbedtls_x509write_crt_der( mbedtls_x509write_cert *ctx, unsigned char *buf,
     size_t sig_oid_len = 0;
     unsigned char *c, *c2;
     unsigned char hash[64];
-    unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
+    unsigned char sig[SIGNATURE_MAX_SIZE];
     unsigned char tmp_buf[2048];
     size_t sub_len = 0, pub_len = 0, sig_and_oid_len = 0, sig_len;
     size_t len = 0;
diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index d59354dc4..a73a1a021 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -43,11 +43,22 @@
 #include "mbedtls/pem.h"
 #endif
 
+
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }
 
+/*
+ * For the currently used signature algorithms the buffer to store any signature
+ * must be at least of size MAX(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)
+ */
+#if MBEDTLS_ECDSA_MAX_LEN > MBEDTLS_MPI_MAX_SIZE
+#define SIGNATURE_MAX_SIZE MBEDTLS_ECDSA_MAX_LEN
+#else
+#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
+#endif
+
 void mbedtls_x509write_csr_init( mbedtls_x509write_csr *ctx )
 {
     memset( ctx, 0, sizeof( mbedtls_x509write_csr ) );
@@ -163,7 +174,7 @@ int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, s
     size_t sig_oid_len = 0;
     unsigned char *c, *c2;
     unsigned char hash[64];
-    unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
+    unsigned char sig[SIGNATURE_MAX_SIZE];
     unsigned char tmp_buf[2048];
     size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
     size_t len = 0;
diff --git a/programs/pkey/pk_sign.c b/programs/pkey/pk_sign.c
index 7ec46752a..0f08db972 100644
--- a/programs/pkey/pk_sign.c
+++ b/programs/pkey/pk_sign.c
@@ -59,6 +59,16 @@ int main( void )
 #include <stdio.h>
 #include <string.h>
 
+/*
+ * For the currently used signature algorithms the buffer to store any signature
+ * must be at least of size MAX(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)
+ */
+#if MBEDTLS_ECDSA_MAX_LEN > MBEDTLS_MPI_MAX_SIZE
+#define SIGNATURE_MAX_SIZE MBEDTLS_ECDSA_MAX_LEN
+#else
+#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
+#endif
+
 int main( int argc, char *argv[] )
 {
     FILE *f;
@@ -68,7 +78,7 @@ int main( int argc, char *argv[] )
     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
     unsigned char hash[32];
-    unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
+    unsigned char buf[SIGNATURE_MAX_SIZE];
     char filename[512];
     const char *pers = "mbedtls_pk_sign";
     size_t olen = 0;